lib/MC/MCMachOStreamer.cpp

   1 //===- lib/MC/MCMachOStreamer.cpp - Mach-O Object Output ------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #include "llvm/MC/MCStreamer.h"
  11
  12 #include "llvm/MC/MCAssembler.h"
  13 #include "llvm/MC/MCContext.h"
  14 #include "llvm/MC/MCCodeEmitter.h"
  15 #include "llvm/MC/MCExpr.h"
  16 #include "llvm/MC/MCInst.h"
  17 #include "llvm/MC/MCObjectStreamer.h"
  18 #include "llvm/MC/MCSection.h"
  19 #include "llvm/MC/MCSymbol.h"
  20 #include "llvm/MC/MCMachOSymbolFlags.h"
  21 #include "llvm/MC/MCSectionMachO.h"
  22 #include "llvm/MC/MCDwarf.h"
  23 #include "llvm/Support/Dwarf.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 #include "llvm/Target/TargetAsmBackend.h"
  27 #include "llvm/Target/TargetAsmInfo.h"
  28
  29 using namespace llvm;
  30
  31 namespace {
  32
  33 class MCMachOStreamer : public MCObjectStreamer {
  34 private:
  35   virtual void EmitInstToData(const MCInst &Inst);
  36
  37 public:
  38   MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
  39                   raw_ostream &OS, MCCodeEmitter *Emitter)
  40     : MCObjectStreamer(Context, TAB, OS, Emitter) {}
  41
  42   /// @name MCStreamer Interface
  43   /// @{
  44
  45   virtual void InitSections();
  46   virtual void EmitLabel(MCSymbol *Symbol);
  47   virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
  48                                    MCSymbol *EHSymbol);
  49   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
  50   virtual void EmitThumbFunc(MCSymbol *Func);
  51   virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
  52   virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
  53   virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
  54   virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
  55                                 unsigned ByteAlignment);
  56   virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
  57     assert(0 && "macho doesn't support this directive");
  58   }
  59   virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
  60     assert(0 && "macho doesn't support this directive");
  61   }
  62   virtual void EmitCOFFSymbolType(int Type) {
  63     assert(0 && "macho doesn't support this directive");
  64   }
  65   virtual void EndCOFFSymbolDef() {
  66     assert(0 && "macho doesn't support this directive");
  67   }
  68   virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
  69     assert(0 && "macho doesn't support this directive");
  70   }
  71   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
  72     assert(0 && "macho doesn't support this directive");
  73   }
  74   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
  75                             unsigned Size = 0, unsigned ByteAlignment = 0);
  76   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
  77                               uint64_t Size, unsigned ByteAlignment = 0);
  78   virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
  79   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
  80                                     unsigned ValueSize = 1,
  81                                     unsigned MaxBytesToEmit = 0);
  82   virtual void EmitCodeAlignment(unsigned ByteAlignment,
  83                                  unsigned MaxBytesToEmit = 0);
  84
  85   virtual void EmitFileDirective(StringRef Filename) {
  86     // FIXME: Just ignore the .file; it isn't important enough to fail the
  87     // entire assembly.
  88
  89     //report_fatal_error("unsupported directive: '.file'");
  90   }
  91
  92   virtual void Finish();
  93
  94   /// @}
  95 };
  96
  97 } // end anonymous namespace.
  98
  99 void MCMachOStreamer::InitSections() {
 100   SwitchSection(getContext().getMachOSection("__TEXT", "__text",
 101                                     MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 102                                     0, SectionKind::getText()));
 103
 104 }
 105
 106 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
 107                                           MCSymbol *EHSymbol) {
 108   MCSymbolData &SD =
 109     getAssembler().getOrCreateSymbolData(*Symbol);
 110   if (SD.isExternal())
 111     EmitSymbolAttribute(EHSymbol, MCSA_Global);
 112   if (SD.getFlags() & SF_WeakDefinition)
 113     EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
 114   if (SD.isPrivateExtern())
 115     EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
 116 }
 117
 118 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 119   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 120
 121   // isSymbolLinkerVisible uses the section.
 122   Symbol->setSection(*getCurrentSection());
 123   // We have to create a new fragment if this is an atom defining symbol,
 124   // fragments cannot span atoms.
 125   if (getAssembler().isSymbolLinkerVisible(*Symbol))
 126     new MCDataFragment(getCurrentSectionData());
 127
 128   MCObjectStreamer::EmitLabel(Symbol);
 129
 130   MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
 131   // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
 132   // to clear the weak reference and weak definition bits too, but the
 133   // implementation was buggy. For now we just try to match 'as', for
 134   // diffability.
 135   //
 136   // FIXME: Cleanup this code, these bits should be emitted based on semantic
 137   // properties, not on the order of definition, etc.
 138   SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
 139 }
 140
 141 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 142   // Let the target do whatever target specific stuff it needs to do.
 143   getAssembler().getBackend().HandleAssemblerFlag(Flag);
 144   // Do any generic stuff we need to do.
 145   switch (Flag) {
 146   case MCAF_SyntaxUnified: return; // no-op here.
 147   case MCAF_Code16: return; // no-op here.
 148   case MCAF_Code32: return; // no-op here.
 149   case MCAF_SubsectionsViaSymbols:
 150     getAssembler().setSubsectionsViaSymbols(true);
 151     return;
 152   default:
 153     llvm_unreachable("invalid assembler flag!");
 154   }
 155 }
 156
 157 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
 158   // FIXME: Flag the function ISA as thumb with DW_AT_APPLE_isa.
 159
 160   // Remember that the function is a thumb function. Fixup and relocation
 161   // values will need adjusted.
 162   getAssembler().setIsThumbFunc(Symbol);
 163
 164   // Mark the thumb bit on the symbol.
 165   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 166   SD.setFlags(SD.getFlags() | SF_ThumbFunc);
 167 }
 168
 169 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
 170   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 171   // MCObjectStreamer.
 172   // FIXME: Lift context changes into super class.
 173   getAssembler().getOrCreateSymbolData(*Symbol);
 174   Symbol->setVariableValue(AddValueSymbols(Value));
 175 }
 176
 177 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
 178                                           MCSymbolAttr Attribute) {
 179   // Indirect symbols are handled differently, to match how 'as' handles
 180   // them. This makes writing matching .o files easier.
 181   if (Attribute == MCSA_IndirectSymbol) {
 182     // Note that we intentionally cannot use the symbol data here; this is
 183     // important for matching the string table that 'as' generates.
 184     IndirectSymbolData ISD;
 185     ISD.Symbol = Symbol;
 186     ISD.SectionData = getCurrentSectionData();
 187     getAssembler().getIndirectSymbols().push_back(ISD);
 188     return;
 189   }
 190
 191   // Adding a symbol attribute always introduces the symbol, note that an
 192   // important side effect of calling getOrCreateSymbolData here is to register
 193   // the symbol with the assembler.
 194   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 195
 196   // The implementation of symbol attributes is designed to match 'as', but it
 197   // leaves much to desired. It doesn't really make sense to arbitrarily add and
 198   // remove flags, but 'as' allows this (in particular, see .desc).
 199   //
 200   // In the future it might be worth trying to make these operations more well
 201   // defined.
 202   switch (Attribute) {
 203   case MCSA_Invalid:
 204   case MCSA_ELF_TypeFunction:
 205   case MCSA_ELF_TypeIndFunction:
 206   case MCSA_ELF_TypeObject:
 207   case MCSA_ELF_TypeTLS:
 208   case MCSA_ELF_TypeCommon:
 209   case MCSA_ELF_TypeNoType:
 210   case MCSA_ELF_TypeGnuUniqueObject:
 211   case MCSA_IndirectSymbol:
 212   case MCSA_Hidden:
 213   case MCSA_Internal:
 214   case MCSA_Protected:
 215   case MCSA_Weak:
 216   case MCSA_Local:
 217     assert(0 && "Invalid symbol attribute for Mach-O!");
 218     break;
 219
 220   case MCSA_Global:
 221     SD.setExternal(true);
 222     // This effectively clears the undefined lazy bit, in Darwin 'as', although
 223     // it isn't very consistent because it implements this as part of symbol
 224     // lookup.
 225     //
 226     // FIXME: Cleanup this code, these bits should be emitted based on semantic
 227     // properties, not on the order of definition, etc.
 228     SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
 229     break;
 230
 231   case MCSA_LazyReference:
 232     // FIXME: This requires -dynamic.
 233     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 234     if (Symbol->isUndefined())
 235       SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
 236     break;
 237
 238     // Since .reference sets the no dead strip bit, it is equivalent to
 239     // .no_dead_strip in practice.
 240   case MCSA_Reference:
 241   case MCSA_NoDeadStrip:
 242     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 243     break;
 244
 245   case MCSA_SymbolResolver:
 246     SD.setFlags(SD.getFlags() | SF_SymbolResolver);
 247     break;
 248
 249   case MCSA_PrivateExtern:
 250     SD.setExternal(true);
 251     SD.setPrivateExtern(true);
 252     break;
 253
 254   case MCSA_WeakReference:
 255     // FIXME: This requires -dynamic.
 256     if (Symbol->isUndefined())
 257       SD.setFlags(SD.getFlags() | SF_WeakReference);
 258     break;
 259
 260   case MCSA_WeakDefinition:
 261     // FIXME: 'as' enforces that this is defined and global. The manual claims
 262     // it has to be in a coalesced section, but this isn't enforced.
 263     SD.setFlags(SD.getFlags() | SF_WeakDefinition);
 264     break;
 265
 266   case MCSA_WeakDefAutoPrivate:
 267     SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
 268     break;
 269   }
 270 }
 271
 272 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 273   // Encode the 'desc' value into the lowest implementation defined bits.
 274   assert(DescValue == (DescValue & SF_DescFlagsMask) &&
 275          "Invalid .desc value!");
 276   getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
 277     DescValue & SF_DescFlagsMask);
 278 }
 279
 280 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
 281                                        unsigned ByteAlignment) {
 282   // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
 283   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 284
 285   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 286   SD.setExternal(true);
 287   SD.setCommon(Size, ByteAlignment);
 288 }
 289
 290 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
 291                                    unsigned Size, unsigned ByteAlignment) {
 292   MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
 293
 294   // The symbol may not be present, which only creates the section.
 295   if (!Symbol)
 296     return;
 297
 298   // FIXME: Assert that this section has the zerofill type.
 299
 300   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 301
 302   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 303
 304   // Emit an align fragment if necessary.
 305   if (ByteAlignment != 1)
 306     new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
 307
 308   MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
 309   SD.setFragment(F);
 310
 311   Symbol->setSection(*Section);
 312
 313   // Update the maximum alignment on the zero fill section if necessary.
 314   if (ByteAlignment > SectData.getAlignment())
 315     SectData.setAlignment(ByteAlignment);
 316 }
 317
 318 // This should always be called with the thread local bss section.  Like the
 319 // .zerofill directive this doesn't actually switch sections on us.
 320 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
 321                                      uint64_t Size, unsigned ByteAlignment) {
 322   EmitZerofill(Section, Symbol, Size, ByteAlignment);
 323   return;
 324 }
 325
 326 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
 327   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 328   // MCObjectStreamer.
 329   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
 330 }
 331
 332 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 333                                            int64_t Value, unsigned ValueSize,
 334                                            unsigned MaxBytesToEmit) {
 335   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 336   // MCObjectStreamer.
 337   if (MaxBytesToEmit == 0)
 338     MaxBytesToEmit = ByteAlignment;
 339   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
 340                       getCurrentSectionData());
 341
 342   // Update the maximum alignment on the current section if necessary.
 343   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 344     getCurrentSectionData()->setAlignment(ByteAlignment);
 345 }
 346
 347 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
 348                                         unsigned MaxBytesToEmit) {
 349   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 350   // MCObjectStreamer.
 351   if (MaxBytesToEmit == 0)
 352     MaxBytesToEmit = ByteAlignment;
 353   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
 354                                            getCurrentSectionData());
 355   F->setEmitNops(true);
 356
 357   // Update the maximum alignment on the current section if necessary.
 358   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 359     getCurrentSectionData()->setAlignment(ByteAlignment);
 360 }
 361
 362 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
 363   MCDataFragment *DF = getOrCreateDataFragment();
 364
 365   SmallVector<MCFixup, 4> Fixups;
 366   SmallString<256> Code;
 367   raw_svector_ostream VecOS(Code);
 368   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
 369   VecOS.flush();
 370
 371   // Add the fixups and data.
 372   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 373     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 374     DF->addFixup(Fixups[i]);
 375   }
 376   DF->getContents().append(Code.begin(), Code.end());
 377 }
 378
 379 void MCMachOStreamer::Finish() {
 380   EmitFrames(true);
 381
 382   // We have to set the fragment atom associations so we can relax properly for
 383   // Mach-O.
 384
 385   // First, scan the symbol table to build a lookup table from fragments to
 386   // defining symbols.
 387   DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
 388   for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
 389          ie = getAssembler().symbol_end(); it != ie; ++it) {
 390     if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
 391         it->getFragment()) {
 392       // An atom defining symbol should never be internal to a fragment.
 393       assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
 394       DefiningSymbolMap[it->getFragment()] = it;
 395     }
 396   }
 397
 398   // Set the fragment atom associations by tracking the last seen atom defining
 399   // symbol.
 400   for (MCAssembler::iterator it = getAssembler().begin(),
 401          ie = getAssembler().end(); it != ie; ++it) {
 402     MCSymbolData *CurrentAtom = 0;
 403     for (MCSectionData::iterator it2 = it->begin(),
 404            ie2 = it->end(); it2 != ie2; ++it2) {
 405       if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
 406         CurrentAtom = SD;
 407       it2->setAtom(CurrentAtom);
 408     }
 409   }
 410
 411   this->MCObjectStreamer::Finish();
 412 }
 413
 414 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
 415                                       raw_ostream &OS, MCCodeEmitter *CE,
 416                                       bool RelaxAll) {
 417   MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
 418   if (RelaxAll)
 419     S->getAssembler().setRelaxAll(true);
 420   return S;
 421 }